Memberane type electron tube analogue device



July 26, 1949. J. w. CLARK MEMBRANE TYPE ELECTRON was ANALOGUE n'svxcn Filed March 17, 1948 2 Sheets-Sheet 1 day/v 14 CLARA July 26, 1949. J. w. CLARK 2,477,115

' MEMBRANE TYPE ELECTRON TUBE ANALOGUE DEVICE Filed March 17, 1948 2 Sheets-Sheet 2 FIG. 6. 7

(Iitorneg Patented July 26, 1949 MEMBRANE TYPE ELECTRON TUBE ANALOGUE DEVICE John w. Clark, Cedar ltapids, Iowa,

Collins Badio Company, 'Cedar Rapids,

corporation of Iowa assignor to Iowa, a

Application m 11, ms, Serial No. 15.405 so Claims- (01. 35-19) This invention relates to electro-mechanical apparatus, and more especially it relates to such apparatus for demonstrating and/or pretermining the operational characteristics of electron tubes and the like.

A principal object of the invention relates to an improved electron tube design apparatus of the deformable membrane type.

Another object is to provide an improved deformable membrane device for use in the desi n of electron tubes, which device is capable of representing electron tube dynamic operating conditions as well as static operating conditions.

Another object is to provide an improved deformable membrane device which can be used in the design or predetermination f the operational characteristics of electron tubes which are to be used at very high frequencies where the phenomena of electron transit time is of considerable importance.

A feature of the invention relates to a device having a deformable membrane of rubber or other similar material, in conjunction with a series of membrane deforming members which are analogues of electron tube electrodes; and with means for motionally vibrating one or more of said members to simulate electric potential variations in a corresponding analogous tube electrode.

Another feature relates to a device or the rubber membrane type having a novel vibratory structure for simulating the dynamic variations of potential between a cathode and a cooperating electrode, such for example as a control grid of an electron tube.

A further feature relates to a device of-the rubber membrane type having a novel vibratory structure for deforming the membrane at a predetermined rate related to the dynamic potential variations between the cathode and cooperating electrode of an electron tube; together with means for automatically releasing one or more balls representing emitted electrons, in a predetermined time relation with respect to the timing of said deformation, so as to simulate dynamic electron transit time conditions in an electron tube.

Another feature relates to an improved device for studying analogous electron trajectories of anelectron tube.

A further feature relates to the novel organization, arrangement and relative location and interconnection of parts for predetermining or studying the action of electron tubes, particularly those designed for use at very high frequencies of which the so-called "Resnatron" 'tube is typical.

Other features and advantages not particularly enumerated, will be apparent after a considerstion of the following detailed descriptions and the appended claims.

In the drawin Fig. 1 is a respective view of the device according to the invention.

Fig. 2 is an enlarged side view of the cathode analogue vibrating and ball releasing mechanism of Fig. 1.

Fig. 3 is a partial sectional view of Fig. 2 taken along the line 33 thereof.

Fig. 4 is a partial sectional view of Fig. 3 taken along the line 4-4 thereof.

Fig. 5 is an enlarged detail of the contacl'or cone shown in Fig. 1.

Fig. 6 is a schematic plan view of the device.

Fig. 7 is a schematic side view of Fig. 6.

Fig. 8 is a schematic electrical diagram showing the circuit connections that may be used with the device of Fig. 1.

Fig. 9 is a graph explanatory of certain features of the invention. e

In recent years. taut rubber membranes-have been rather widely used to study the action of grid controlled electron tubes. However these prior devices have been limited in their use in two rather important respects; one, they can simulate only the static potential conditions within a tube; two, they cannot be used accurately to predetermine or represent the actual conditions in tubes which are to operate at very high frequencies at which the electron transit time effect must be taken into account. One of the types of very high frequency tubes which has been studied in recent years is the so-called Resnatron tube, one form of which is described in detail in United States Letters Patent No. 2,405,763. While the present invention finds a peculiar adaptability to the study and design of that type of tube, it is to be understood that the invention is capable of use in connection with the design or operational determinations of the dynamic characteristics of any other kind of electron tube. Furthermore, the transit time analogous operation of the device according to the invention, is useful in connection with the design or study of any electron tube where transit time effects must be taken into account.

- I have found that the transit time conditions in an electron tube can be analogously represented or'set up in a rubber membrane device by oscillating one or more members transversely with respect to the membrane to deform the slope of the membrane at a particular rate, and this rate can be made functionally analogous to the dynamic electron transit time conditions in any given tube or between any given arrangement of electrodes and their respective dynamic electrical excitations. One of the most important things that it is necessary to know in deslgning and st ying electron tubes, especially those to be ravity towards the used at very high frequencia. is the trajectories which the electrons follow from the instant they leave the cathode until they arrive at, or pass. one or more succeeding electrodes within the tube. Heretofore these trajectories have been studied by placing one or more members in contact with a stretched rubber membrane so as to deform it downwardly out of a horizontal plane, the amount of such deformation representing the static potential gradient between one electrode, for example an anode. and a cathode. In order to determine these traiectories, the electrons have been represented by small metal balls which are releasedat the "high" part of the membrane, and the slope of the membrane and its configuration cause these balls to roll by member which represents the anode. While such an arrangement is great utility in studying tube designs for operation at relatively low radio frequency, it is not simulating dynamic or variable potential conditions. For this reason it has not been used satisfactorily heretofore to study or design tubes which must be operated at very high radio frequencies.

The device according to the invention overcomes the limitations of these prior rubber membrane .devices. As shown in Fig. 1, it comprises a rigid metal frame I having rigid metal uprights 2-5 at the corners thereof. Rlgidly fastened to the uprights 2l is another rigid horizontal metal frame 8 across which is stretched the deformable membrane 1 of rubber or other similar stretchable material. The membrane 7 has attached to its periphery a series of small pulleys 8. and the arms of frame i have a series of similar but staggered small pulleys Q. The wire cord or thin cable ii is looped in zigzag fashion between the various pulleys and the ends of this cord or cable are tied together. By pulling on the ends of this cord before tying them, the membrane I is uniformly stretched in all directions in a horizontal plane, so that the tension per unit area of the membrane is uniform throughout. Normally, therefore, the membrane assumes a perfectly horizontal position in its stretched condition, and if desired, the frame i or the frame 8 can be provided with suitable adjustments at the corners to insure that the stretched membrane is perfectly horizontal. It will be understood that the invention is not limited to the particular manner of uniformly tensioning the membrane as above described.

Extending between the uprights 2 and I is a guide rod H, and a similar guide rod l2 extends between the uprights 3 and t. Slidably mounted on the rods ii, l2, are a series of cross arms lll$. Slidably attached to arm I! are two brackets ll, it, each having at its forward end a collar I9, 20, for slidably receiving a rod 2!. 22, rigidly attached to a respective U-shaped member 23. 24. By this arrangement, therefore, the members 28 and 24 can be adjusted vertically and horizontally with relation to the membrane 1. Preferably the brackets i1 and II are not rotatable around the arm II, so that the vertical position of members 23 and 24 is controlled by loosening the thumb nuts 25. .26, and moving the members 23, 24, in a vertical direction. when the proper vertical positions have been chosen for members 23, 24, they are fastened in place by thumb nuts 25, 28.

Likewise carried by arm I are two brackets 21. 2|, which support rod 28 (see Fig. 5). Preferably rod II is electrically insulated from the brackets 4 by intervening insulator bushings II, II. Extending parallel to rod 28, but in spaced relation rearwardly thereof. is a wire I2 which is conductively attached to brackets 21, 2!. Downwardly depending from rod II is a series of spaced thin flexible metal fingers It which extend almost to the membrane I so as to be freely swin able without touching the membrane. Normally therefore, there is no electrical contact between any of the fingers I! and the wire 32. However, when any of the fingers is deflected rearwardly, it completes an electrical circuit for purposes to be described.

slidably keyed to arm I i are similar brackets 34, II, which slidably receive vertical rods 38, 31, rigidly attached to respective L-shaped members 38, 38. Members 3|, II are locked in adjusted vertical position by the respective thumb nuts 40, I I. Similarly, there are slidably keyed to arm Ii. brackets l2, G3 which slidably receive the rods 44, lb, rigidly attached to the U-shaped member I, which can be held in adjusted vertical position by corresponding wing nu Mounted adjacent the forward end of frame i is a platform 41 to which is fastened a suitable electric motor 48 which, by means of pulleys 4!, SI. drives a disc ll having an eccentric pin 52 coupled by link 83 to a rigid metal arm 54. Ann 84 has fastened thereto, intermediate its ends. a downwardly depending bracket ll having a circular bearing lug it supported on shaft II, which is also supported in a pair of bearing brackets 58. 58, fastened to platform 41.

Rigldly fastened to the lower end of bracket 58 is another rigid metal arm 86 which extends parallel to arm '4. Arms I and 00 extend rearwardly to a position in front of the members 23. 24, with the arm ll above the membrane 1 and with the arm Bl below the membrane. Arm I I has rigidly attached thereto a transversely extending bar ll (see Fig. 2) at the opposite ends of which there are attached the right-angled metal plates '2, 83. Likewise attached to the rear of arm 60 is a transverse bar 64 which carries at opposite ends a pair of right-angled metal plates similar to plates l2, l3, but only one of which is shown in Fig. 2, namely plate 85.

Plates 82 and "are adjustabl'y fastened to their respective bars I and N so that the membrane l is firmly clamped between the opposing horizontal faces of plates 82 and II. Likewise the membrane is clamped between the corresponding opposed horizontal members of the other pair of right-angled plates.

Fastened to the rear end of arm II by a threaded rod 86 and its fastening nuts 01, is a ball releasing magazine consistlng of a hollow metal box-like member II which has a series of circular windows in its upper wall, and attached to this upper wall in alignment with each-window is a corresponding series of vertically extending tubular magazine members I8, ll, etc. While the drawing shows only two of these vertically extending magazine members. it will be understood that any deslred number may be employed.

'The rear face H of the box member 88 (see Figs. 3 and 4) has a series of windows 12, 13, equal in number to the tubular members 89, I0, but oil'set laterally therefrom a distance slightly greater than the diameter of the balls 14 which are loaded into the tubular members 89, ll. Slidable within the box-like member is a shutter member I! having a series of U-shaped perforations 10, I1, etc., there being one of these perforations for each of the tubular members 69. ll, etc.

, The member 18 is adapted to bereciprocated under control of a plate I8 which carries at one end a pin I8 fitted into a corresponding opening in the member I8. The upper wall of member 88 is provided with a pair of slots 88 to accommodate the-pins 19 so as to permit the member I8 to be reciprocated horizontally, thus moving the shutter member I5 likewise. Consequently, when the member I8 is in the position shown in Figs. 3 and 4, a single ball is in each of the perforations I8, 11, but the balls are not aligned with the exit openings 12, 13. On the other hand, when the member 18 is moved to the left, it brings a single ball from each tubular magazine 88, 18, etc., into alignment with the corresponding exit opening I2, I3, in the rear wall 1| of box-like member 88,

thus allowing a set of balls to freely leave the said member simultaneously and roll down the inclined portion of the membrane I. The degree of inclination of the membrane I at the exit points of the balls from the magazine is controlled by the initial bias which is placed upon the membrane I by the initial adjustment of the plates 82, 83, and their cooperating plates underneath the surface of the membrane, and/or by the initial adjustment of the vertical position of the plates 23, 24'. In other words, when the arms 84 and 88 are in their normal position. represented for example by the dotted line relation shown in Fig. 2, the membrane I can be biased so as to have a downward slope from the exit end of the ball magazine towards the members 23 and 24.

For the purpose of operating the ball release member or shutter 15 in timed relation to the rotation of disc 5|, there is provided an electromagnet 8| which is rigidly attached to the arm 54. The armature 82 of this electromagnet carries a right-angled member 83, the free end of which engages in a slot in the plate 18. Consequently, as the armature 82 is operated by its electromagnet, it moves the arm 83 so as to cause the plate I8 to move either to the right or to the left. For example, when the magnet 8| is deenergized, the shutter member 15 is in the position shown in Figs. 3 and 4, and when the said magnet is energized, the shutter member I5 is moved to the left to allow a single ball to be released from each of the exit apertures By reason of the foregoing arrangement, it will be clear that only one set of horizontally spaced balls can be simultaneously released from the magazine and the time interval between release of successive sets is determined by the rate of energization of the electromagnet 8|. Preferably the circuit for operating the electromagnet 8| is controlled by a suitable cam or contact mechanism which is operated by motor 48 in timed relation to the operation of arms 54 and 88. Thus as shown in Fig. 8, the motor 48 also drives a wheel 84 having a cam-like projection 88 on its periphery which cooperates with a pair of normally open contacts 88 which control the energization of the magnet 8!. The projection 85 occupies only a small portion of the angular periphery of wheel 84, and since wheel 84 is operated by the same motor which operates the arms 54 and 88, it is clear that the circuit of magnet 8| will be closed for only a small instant of time during the complete cycle of oscillation of w the said arms. Thus it is possible by adjusting the wheel 84 on its shaft, to close the contacts 88 at any particular instant of time with respect to the oscillatory deformation of the membrane 1 as graphically illustrated in Fig. 9. In other words, the contacts 88 can be closed at any in- 8 stant. during the complete oscillatory cycle of deformation of the membrane I.

From the foregoing description it will be seen that when the motor is in operation, the arms 84 and 88 oscillate as a unit around the shaft II as a pivot, and in doing so, they vibrate the membrane I between the dotted line positions represented in Fig. I. The rate of this mechanical vibration of the membrane I is, in accordance with the invention, related in a predetermined manner to the frequency of the radio frequency signals which are to be impressed, for example, on the control grid of a tube. Thus the ball magazine would be the analogue of the electron emitting cathode of an electron tube and the balls would be the analogue of the emitted electrons, and the members 23, 24, would be the analogue of a control grid of this tube. However or convenience, instead of vibrating the control grid members 23, 24, to represent the radio fre quenc'y variations of grid potential, the ball magazine which represents the cathode is vibrated through arms 54 and 88 to represent the radio frequency potential gradient between the cathode and control grid. In order to study the action of a tube having a predetermined negativebias on the control grid, for example a class Oamplifler, it is usual to bias the control grid negatively so that electrons do not proceed from the cathode to the anode of the tube except during predetermined portions of each radio frequency cycle. For this reason, the balls may be discharged from the magazine at predetermined instants during each vibration of the arms 84 and 88.

The particular device illustrated in Fig. 1 is intended to study the operation of a high power ultra high'frequency tetrode in which event the members 23, 24, would correspond to the control grid of such a tetrode, the members 38 and 88 wouldthen correspond to the shield grid, and the member 48 would correspond to the'anode; The shield grid analogue members 38, 39, and the anode analogue'member 48 would then be adjusted vertically so as to produce between the cathode analogue member and the anode analogue member a predetermined slope in the membrane I which would correspond to the normal potential gradient between the cathode and anode of the tetrode. Likewise, the members 38 and 38 would be adjusted vertically to control this potential gradient to correspond with the electrical parameters of the tube under study. In Fig. 'I the rate of mechanical oscillation of the membrane 1 by the cathode analogue members 82-85 is represented by the letter "1. The letter A represents the horizontal scale factor of the device in proportion to the actual electrode spacing between cathode and anode in the tube under study. The letter "3 represents the vertical scale factor, that is, the number of centimeters corresponding to a given voltagegradient between the cathode and anode, and thus represents the vertical scale factor of the device.

I have found that it is possible to represent with substantially complete accuracy the various electron trajectories for a given arrangement of electrodes and their potentials by following the following formula:

;=12oor1 vF A where 7 Jr is the radio frequency in thousands of megacycles (kmc):

A is the horizontal scale factor of the model written as a number greater than 1:

B is the vertical scale factor of the model in cm.

per kilovolt.

It will be understood, of course, that the scale factors or dimensions A and B of the device can be made of any desired range. As a specific example, it has been found that where the frequency i1 is 3,000 megacycles, this condition can be accurately simulated by mechanically oscillating the arms 54 and 6| at the rate of one cycle per second.

As the balls leave the magazine, they follow trajectories or paths which are determined by the slope and configuration of the membrane. Thus the electrode analogues 23, 24, in addition to providing a gravity gradient to cause the balls to roll towards the anode It, at the same time provide somewhat of a trough-like curvature, thus tending to cause the balls to approach each other which would be analogous to the electron focussing action of a grid opening.

In certain cases it is desirable to ascertain whether the balls of a given released set all reach the vicinity of the screen grid analogues l8, 3! in phase. If they are in phase, they all strike the flexible fingers 33 simultaneously and close a circuit through a suitable indicating meter 84. In other words, meter 84 will show a single indication for each set of released balls all of which arrive in phase at the fingers 33. If, however. one or more balls are delayed in arrival, there will be more than one deflection of the meter M and the time duration between these deflections will serve as an indication of the phase delay between the arriving balls. If desired, each of the spring fingers 33 may be insulated from each other and connected to respective individual meters, so that the action of the several balls can be individually determined in so far as their arrival at the screen grid analogue 3B, 39, is concerned. It will be understood of course that if the arrival phases of the balls at any of the remaining electrodes are to be studied or determined, a similar contactor comb corresponding to elements 32 and 13 may be mounted directly in front of the appropriate electrode.

The invention is not limited to the mechanical vibration of the cathode analogue. For example, if a modulating potential is to be impressed upon any of the tube electrodes, or if their dynamic voltage conditions are to be studied, these mechanical analogues can be vibrated as described above for the cathode analogue.

Inasmuch as the device is in effect a motlonal device. the rolling balls can be photographed by a motion picture camera, the beginning of the camera operation being synchronized in any suitable electrical manner with the release of the balls from the cathode magazine.

While one particular embodiment oi the invention has been described herein, various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a device of the type described, a flexible membrane, means to support said membrane and to tension it substantially uniformly, a pair of electrode analogue members bearing on said membrane to produce therebetween a horizontal inclination in said membrane representing an electric potential gradient, and means to continuously oscillate said ,membrane at a relatively low frequency to represent high frequency variations of said electric Potential.

2. In a device of the type described, a flexible membrane, means to support said membrane and to tension it substantially uniformly, an electronemitting cathode analogue member for releasing balls therefrom representing electrons, another electrode analogue member, means to support both said members in contact with said membrane, and means for mechanically vibrating said membrane between said members to vary its slope to represent a varying electric potential gradient.

3. In a device of the type described, a flexible membrane, means to support said membrane and to tension it substantially uniformly, an electronemitting cathode analogue comprising a ball magazine, means for automatically releasing at least one ball from said magazine to represent an emitted electron, a member in contact with said membrane to produce a downward inclination in said membrane beginning adjacent the exit point of said ball from said magazine, and means for continuously and mechanically vibrating said membrane to vary its slope at a predetermined rate to represent variations of electric potential gradient.

4. A device according to claim 3 in which means are provided for timing the release of said ball from said magazine with relation to the cycle oi. variation of the slope of said membrane.

5. In a device of the type described, a flexible membrane, analogue members for the electronemltting cathode, the control grid and anode of an electron tube, means to support said members in contact with said membrane to produce predetermined slopes therebetween to represent electric potential gradients between the electrodes of said tube, and means to continuously oscillate at least one of said supports at a relatively low frequency to represent high frequency dynamic electric potential variations within the tube.

6. In a device of the type described, a stretched flexible membrane, a plurality of members in contact. with said membrane for producing therein slopes representing potential gradients between the electrodes of a tube, one of said members representing the electron-emitting cathode of the tube, another of said members representing an electron control electrode and another of said members representing an output anode, means for mechanically vibrating said cathode member to represent potential gradient variations between the cathode and control electrode of the tube, a ball release magazine, and means for automatically releasing simultaneously from said magazine a set of balls in timed relation to the vibration of said member.

'7. A device according to claim 6 in which said magazine is movable with said cathode member.

8. In a device of the type described, a flexible membrane, means to support and tension said membrane uniformly in a horizontal plane, a pinrality of members in contact with said membrane and adjustable with relation thereto to produce slopes in the membrane to represent electric potential variations, means to vibrate one of said members to vary the membrane slope to represent variations of electric potential, means to release 9 the relative phase arrival of said balls at the region adjacent said one of said members.

9. A device according to claim 8 in which said electric contact means includes a plurality of deflectable spring contact members which are engaged by said balls during their rolling action, and indication means controlled by said deflectable members.

10. A device for studying the action of ultra high frequency electron tubes, wherein the phenomena of electron transit time is of importance, comprising a stretched flexible membrane, a plurality of members in contact with said membrane and adjustable to produce predetermined slopes in said membrane to represent electric potential gradients, one of said members representing the electron-emitting cathode of said tube, another member representing a grid of said tube, and a third member representing an anode of said tube, means to vibrate said one of said members mechanically at a rate bearing a predetermined relation to the radio frequency potentials existing upon the grid of said tube, and means associated with said one member to release at least one ball which rolls from said one member down said membrane towards said anode member to represent an electron trajectory.

11. A device according to claim 10 in which shutter means are provided for releasing said ball in a predetermined timed relation with respect to the mechanical vibration of said one member.

12. A device according to claim 10 in which said one member has associated therewith a ball magazine for releasing simultaneously a series of balls.

13. In a device of the character described. means for simulating the dynamic electrical conditions within an electron tube, including a ball magazine having a series of openings for releasing a series of balls simultaneously to represent emitted electrons, a shutter member for controlling the release of said balls, a stretched rubber membrane along which said balls roll after release, and means to vibrate said membrane mechanically at a rate to simulate the dynamic potential gradients acting on said electrons.

14. A device according to claim 13 in which said shutter member is provided with an electromagnet for operating it to release said balls, and

means are provided for mechanically vibrating said diaphragm at a predetermined rate and including circuit connections for energizing said electromagnet at a predeterminedrate with respect to the rate of vibration of said membrane.

15. In a device of the type described, comprising a substantially horizontal stretched rubber membrane, a plurality of members in contact with said membrane and spaced horizontally thereof from each other a distance bearing a predetermined relation to the interelectrode spacing of an electron tube under study, one of said members being a cathode analogue member, another member being a control grid analogue member for producing in said membrane an inclination between the cathode analogue member and the control grid analogue member which inclination represents the potential gradient between the cathode and control grid of said tube, a third member representing the anode of said tube, means associated with said cathode analogue member to release in phase a plurality of balls which roll down said membrane and past said control grid analogue member towards said anode, said control grid analogue member being shaped and being held against said membrane to cause said balls to simulate the focussing action on the electrons of the tube under study, and means to vibrate mechanically said cathode analogue member at a relatively low frequency rate representing the high frequency dynamic potential variations on the gridof said tube.

16. A device according to claim 15 in which means are provided for automatically releasing said balls at a predetermined point during the cycle of the vibration of said membrane.

17. A device according to claim 13 in which each magazine comprises a series of vertical tubes each containing a plurality of balls, said tubes being attached to a substantially horizontalboxlike member having a series of exit openings one for each tube but offset laterally therefrom, said shutter member being slidable within said boxlike member and having a series of similar openings one for each of said tubes, and means to move said shutter member to one position to allow a single ball from each tube to enter said box-like member and to move said shutter member to another position to allow each of said single balls to emerge from a corresponding one of said exit openings.

18. A device according to claim 13 in which the means to vibrate said membrane comprises a member in contact with the under surface of the membrane and another member in contact with the corresponding upper surface of the membrane, both said members being movable as a unit with said membrane.

19. A device for analogously representing the dynamic conditions within an electron tube, comprising a stretched flexible horizontal membrane, a plurality of spaced members representing respective tube electrodes and being in contact with said membrane, the horizontal spacings between said members bearing a predetermined ratio to the interelectrode spacings of said tube, means to hold said members against said membrane to impart verticalslopes to the membrane in the regions between said members "which slopes bear a predetermined ratio to the electric potential gradients between the electrodes of the tube. means for mechanically and continuously oscillating one of said members at a relatively low frequency representing the high frequency of the electrical potential impressed upon one of the electrodes of the tube.

20. A device according to claim 19 in which said one of said members is vibrated mechanically at a frequency I in accordance with the formula where I is the mechanical frequency of vibration in cycles per sesond; fl is the electrical excitation frequency of the corresponding electrode of the tube under study; A isthe horizontal scale factor relating the horizontal spacing of said members to the electrode spacings of the tube; B is the vertical scale factor representing the slope of the membrane in terms of electric potential gradient between the tube electrodes.

JOHN W. CLARK.

Banzai-moss crrnn The following references are of record in t file of this patent:

Bell Laboratories Record. May 1938, vol., XVI, No. 9, pages 305-809.

The Electrostatic Electron Multiplier-reprinted from Proceedings of the I. R. 12., vol. 27, No. 9, September 1939. 

